1. Field of the Invention
The present invention relates to an improved capacitor. More specifically, it relates to improved capacitor having wide foil leads.
2. Description of the Prior Art
The use and structure of conventional powder coated disk shaped capacitors is extremely well known. Such capacitors have been routinely utilized for decades in transistor radios, televisions and a variety of electrical devices. Such capacitors, however, typically utilize some type of a wire having a circular cross sectional configuration as the leads to the capacitors electrodes. The leads are utilized to connect (often by soldering) the capacitor into the electrical circuit for which its capacitance function is needed or desired.
While such conventional disk shaped capacitors are generally effective, the use of leads having a circular cross-sectional configuration often creates inductance which precludes the capacitor from effectively operating at high frequencies up to and above 1 gigahertz. To function effectively at giga-hertz frequencies, capacitors must have minimum series inductance, otherwise they effectively become an inductor and present a high lagging rising reactance, rather that the low leading declining reactance required by the circuit. Further, because the existing practice of positioning the two round leads relatively close together in a generally parallel orientation creates difficulties in mounting the capacitor into some circuit configuration.
Holtzman, U.S. Patent suggests the use of a interconnection elements 14 and 16 (which can include a foil member) to interconnect different sections of a multi-section capacitor. The conductive sleeve 14 can be a folded piece of foil material similar to that of the capacitor electrodes and the tab 16 is a flexible foil like material. The structure of the interconnection elements 14 and 16 is best shown in FIG. 3B. To applicant""s knowledge, the use of a single unfolded piece of foil as a lead for a disk shaped capacitor has never previously been proposed.
Thus, there remains a need for a disk shaped capacitor which can be safely utilized at high frequencies up to 1 gigahertz and there further remains a need for such a capacitor which has lead orientations which allow for connection to a variety of electrical circuits.
The present invention provides a disk shaped capacitor which has low impedance and can be effectively utilized at high frequencies up to 1 gigahertz. The present invention also provides a capacitor which can be formed with a variety of lead orientations to allow for easy connection to a variety of electrical circuits.
It has been well known for over a century that the self-inductance of a wide flat lead is lower than that of a thin round wire. This results since a current in round wire creates an optimum field for energy storage and hence a high inductance, whereas the current flows in a flat lead produce fields which cancel each other out, other than at the edges, and therefore have a lower capability for field energy storage and thus lower inductance.
In its simplest form, the present invention provides a capacitor comprising an electrically insulating ceramic disk having a top and bottom surface and a center axis; a first disk shaped electrode mounted to said top surface; a second disk shaped electrode mounted to said bottom surface; a first lead connected to said first electrode and a second lead connected to said second electrode, said first lead and said second lead each being formed of wide flat strips of an electrically conducting foil whereby said leads provide low inductance and allow the capacitor to effectively perform at high frequencies up to 1 gigahertz; and a powder coated outer layer covering said ceramic disk, first electrode and second electrode and a connecting end of said first lead and said second lead. As used in this patent application, a xe2x80x9cwidexe2x80x9d strip of electrically conducting foil shall refer to any lead which has a width dimension at least 20% of the diameter of the electrically insulating ceramic disk. As used in this patent application, a xe2x80x9cflatxe2x80x9d strip of electrically conducting foil shall refer to any lead which has a thickness greater than or equal to the thickness of the electrode to which it is attached.
Preferably, the electrodes are formed of palladium silver and are formed to a thickness of about 0.005 inches.
Below, a variety of lead orientations are disclosed. As will be apparent to those of skill in the art, the particular lead orientation which is preferred will depend almost entirely upon the space constraints, and locations where the leads will need to be attached to a particular electrical circuit.
In one embodiment, said first lead and said second lead extend axially outward from said first electrode and second electrode, respectively, and wherein said first lead and said second lead are situate in a single plane.
In another embodiment, said first lead and said second lead extend axially outward from said first electrode and second electrode, respectively, and wherein said first lead and said second lead are situate, respectively, in planes which are transverse to one another.
In yet another embodiment, said first lead and said second lead extend radially outward from said first electrode and second electrode, respectively, at radial angles approximately 90 degrees apart from one another and wherein said first lead and said second lead are situate, respectively, in closely spaced apart parallel planes.
In yet another embodiment, said first lead and said second lead extend radially outward from said first electrode and second electrode, respectively, at radial angles approximately 180 degrees apart from one another and wherein said first lead and said second lead are situate, respectively, in closely spaced apart parallel planes.
In the preferred embodiment of the invention said first lead and said second lead each have a width in the range of 50% to 80% of a diameter of the electrically insulating ceramic disk. Preferably, said first lead and said second lead each have a width which is approximately 70% of a diameter of the electrically insulating ceramic disk. Preferably, the foil leads are forms of copper.